The present invention relates to flexible tubes which can be favorably employed as a forceps channel or biopsy channel in an endoscope or a tool channel in a borescope. The invention is more particularly directed to flexible tubes which can be bent in rather tight circles without kinking, and which are gas- and liquid-tight.
Medical endoscopes, such as colonoscopes and gastroscopes, have elongated, flexible insertion tubes which can be inserted into a patient for observation and treatment of diseased tissues within e.g. the stomach or intestine. A biopsy channel or forceps channel extends within the endoscope insertion tube to permit an elongated medical instrument to be inserted through the endoscope into the viewing area thereof for removal or cauterization of tissue.
The path of the endoscope into the body is often rather tortuous, so the biopsy channel should be constructed to be highly flexible. Moreover, the channel must retain its open cross section and not kink when the channel flexes. The channel must also be impervious to fluids, so that fluids from the body tissues do not contact the insertion tube except at its outer sheath and inner surface of the channel. The channel and sheath should be sterilizable by flushing with guteraldehyde or the like.
One flexible tube for use as an endoscopic forceps channel is described in U.S. Pat. No. 4,279,245. In that case the tube is formed of a tubular crystalline fluoropolymer resin, such as PTFE to which is added a synthetic resin filler to make the tube gas-tight and water-tight. The filler resin enters the pores and interstices between PTFE fibrils from the outside of the tube and seals these gaps to a controlled depth. This tube is rather difficult to construct and, because the gaps among the PTFE fibrils are not open, but filled at and near the exterior surface, the tube is not as flexible as desirable.